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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

45444 results found.

  1. Swift GRB 250225B: Global MASTER-Net observations report
  2. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  3. Fermi GRB 250226A: Global MASTER-Net observations report
  4. Fermi trigger No 762205158: Global MASTER-Net observations report
  5. GRB 250226A: Fermi GBM Final Real-time Localization
  6. EP250225a: Global MASTER-Net observations report
  7. EP250225a: GSP optical upper limit
  8. EP250223a: GMG Optical Observation
  9. EP250225a: Einstein Probe detected of a fast X-ray transient
  10. Fermi GRB 250225A: Global MASTER-Net observations report
  11. GRB 250225B: Swift detection of a burst
  12. EP250223a: GROWTH-India Telescope optical observations
  13. GRB 250221A: Swift-BAT refined analysis
  14. GRB 250223C: SVOM/GRM observation of a long burst
  15. EP250215A: J band upper limit by SYSU 80cm telescope
  16. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  17. GRB 250225A: Fermi GBM Final Real-time Localization
  18. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  19. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  20. EP250223a: Kinder optical follow-up observations
  21. GRB 250207a: ATCA Radio Upper Limits
  22. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  23. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  24. GRB 250119B: VZLUSAT-2 detection
  25. GRB 250223C: Fermi GBM Final Real-time Localization
  26. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  27. GRB 250202B: VZLUSAT-2 detection
  28. GRB 250219A: EP-FXT afterglow detection
  29. EP250223a: GOTO optical afterglow detections
  30. GRB 250222A: SVOM/GRM observation of a burst
  31. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  32. GRB 250210A: VZLUSAT-2 detection
  33. GRB 250206A: VZLUSAT-2 detection
  34. EP250223a: REM NIR upper limit
  35. EP250223a: TRT optical afterglow observation
  36. EP250223a: refined analysis of the EP-WXT and FXT observations
  37. EP250223a: 1.6m Mephisto and 50cm array observations
  38. GRB 250221A: TNOT detection of the optical counterpart
  39. EP250223a: SVOM/VT optical observation
  40. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  41. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  42. The EP-WXT trigger 01709131882 is likely a flaring star
  43. EP250223a: OASDG optical observations
  44. EP250223a: LCO detection of the afterglow
  45. EP250223a: early optical detection by BOOTES-4
  46. EP250223a: NOT redshift z = 2.756
  47. EP250223a: Swift/XRT localization
  48. EP250223a: NOT optical afterglow candidate
  49. GRB 250223B: Fermi GBM Final Localization
  50. EP250223a: Global MASTER-Net observations report
  51. GRB 250221A: VLA radio detection
  52. Fermi GRB 250223A: Global MASTER-Net observations report
  53. Fermi trigger No 762020305: Global MASTER-Net observations report
  54. GRB 250223A: Fermi GBM Final Real-time Localization
  55. EP250223a: Einstein Probe detection of an X-ray transient
  56. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  57. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  58. GRB 250221A: continued Mondy optical observations, brightening afterglow
  59. GRB 250221A: Optical counterpart detection by LCO.
  60. GRB 250221A: Mondy optical observations
  61. Konus-Wind detection of GRB 250221A
  62. GRB 250221A: Assy optical observations
  63. EP250220a: FTW optical and NIR observations and upper limits
  64. EP250220a: EP-FXT follow-up observations
  65. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  66. GRB 250221A: VLT/X-shooter redshift z = 0.768
  67. GRB 250221A: GRANDMA/TAROT Detection
  68. Fermi trigger No 761805304: Global MASTER-Net observations report
  69. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  70. GRB 250221A: Swift-XRT refined Analysis
  71. GRB 250221A: NOT optical observations
  72. GRB 250221A: 1.6m Mephisto optical detection
  73. LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate
  74. GRB 250221A: AKO Optical Upper Limit
  75. GRB 250221A: Swift/UVOT Detection
  76. EP250220a: Liverpool Telescope upper limits
  77. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  78. GRB 250221A: REM optical/NIR afterglow detection
  79. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  80. GRB 250221A: Enhanced Swift-XRT position
  81. LIGO/Virgo/KAGRA S250221eb: Retraction of GW compact binary merger candidate
  82. EP250220a: 1.6m Mephisto observations
  83. EP250220a: Liverpool Telescope optical upper limits
  84. EP250220a: Optical upper limit with Kinder observations
  85. SVOM trigger sb25022102 is not an astrophysical event
  86. SVOM/sb25022102: SVOM detection of an X-ray transient
  87. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  88. GRB 250221A: Swift detection of a burst with an optical counterpart
  89. Swift GRB250221.15: Global MASTER-Net OT detection
  90. Swift GRB250221.15: Global MASTER-Net observations report
  91. EP250220a: Xinglong optical upper limit
  92. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  93. GRB 250220B: Fermi GBM Final Real-time Localization
  94. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  95. GRB 250220A: Fermi GBM Final Real-time Localization
  96. EP250220a: Global MASTER-Net observations report
  97. EP250220a: EP-WXT detection of a fast X-ray transient
  98. Konus-Wind detection of GRB 250217C (short)
  99. GRB 250219A: Swift/UVOT Upper Limits
  100. GRB 250219A: OHP/T193 optical upper limit

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